How can I make a prototype?

Hard to say! Jokes apart, there are many ways to approach the making of a prototype and in the end it really comes down to which one is the best for YOU to create a prototype.
Because of this it's hard to learn that from a book, you rather learn by doing instead, which in the end means failing, and repeating, and iterating over and over to perfect your project and your methodology at the same time!

Also, it really depends on what kind of prototype you are going to work on. In our experience with the opencare project we quickly found ourselves facing a wide variety of possible projects:

Mobile or desktop apps and online services

Artifacts and tools

Physical devices with embedded digital electronics

Interactive devices with analog electronics

Mechanical devices

That said, in this chapter we'll try to give you an overview of what we have found to be a good methodology and useful technologies to prototype hardware solutions using tools and machines like the ones available in a Makerspace or Fablab.